It has been heretofore known to perform operations upon the eye in order to improve nearsightedness. Specifically, a technique known as radial keratotomy has been known wherein radial slits are made upon the exterior of the cornea in order to change the shape of the cornea to improve nearsightedness.
It has recently been proposed to perform operations upon the eye to improve farsightedness by making selected thermal burn spots upon the exterior periphery of the cornea. In this way, the limbal ring of the cornea is effectively constricted or the circumference thereof is reduced in order to change the shape of the cornea in order to improve farsightedness. Such burn spots have been made by heated needles and attempts have also been made to utilize laser beams. However, such efforts have not been totally satisfactory, and the correction has tended not to be long lasting. This is believed to be because the heat generated by the heated needle or the laser beam is diffused or disseminated throughout the surface epithelium of the cornea and does not permanently degrade the stroma. Thus, a need has arisen for a technique for permanently degrading selected areas of the corneal stroma in order to tighten or reduce the circumference of the limbal ring in order to provide the desired correction to the eye.